Development system seal

ABSTRACT

An apparatus in which an electrostatic latent image recorded on an image bearing member is rendered visible. The apparatus is moved from an inoperative position spaced from the electrostatic latent image to an operative position in communication therewith. In the operative position, charged particles are deposited on the electrostatic latent image and a seal prevents charged particles from being distributed external to the apparatus and the image bearing member.

United States Patent [191 Hanson DEVELOPMENT SYSTEM SEAL [75] Inventor: William J. Hanson, Rochester, N.Y.

[73] Assignee: Xerox Corporation, Stamford,

Conn.

[22] Filed: Oct. 23, 1973 [21] Appl. No.: 408,363

[52] US. Cl. 118/8, 118/637, 355/3 DD [51] Int. Cl G03g 13/06 [58] Field of Search 118/7, 8, 637

[56] References Cited UNITED STATES PATENTS 3,608,522 9/1971 Davidson 118/8 3,634,077 1/1972 Sullivan i i 118/637 X 3,671,119 6/1972 Engel et a1 118/637 X [451 Mar. 25, 1975 3,800,743 4/1974 Egnaczak 118/637 X 3,809,012 5/1974 Delvecchio 118/637 Primary ExaminerMervin Stein Attorney, Agent, or Firm-H. Fleischer; J. J. Ralabate; C. A. Green [57] ABSTRACT An apparatus in which an electrostatic latent image recorded on an image bearing member is rendered visible. The apparatus is moved from an inoperative position spaced from the electrostatic latent image to an operative position in communication therewith. 1n the operative position, charged particles are deposited on the electrostatic latent image and a seal prevents charged particles from being distributed external to the apparatus and the image bearing member.

8 Claims, 4 Drawing Figures DEVELOPMENT SYSTEM SEAL BACKGROUND OF THE INVENTION This invention relates generally to an electrophoto- I graphic printing machine, and more particularly concerns an improved development system utilized therein.

In electrophotographic printing, a photosensitive element having a photoconductive insulating layer is charged to a substantially uniform potential. This sensitizes the surface of the insulating layer. The charged photoconductive surface is then exposed to a light image of an original document to be reproduced. In the irradiated areas, the charge is selectivelydissipated in accordance with the light intensity reaching the photoconductive surface. This records an electrostatic latent image on the photoconductive surface corresponding to the original document. Development of the electrostatic latent image is achieved by bringing a developer mix into contact therewith. Typical developer mixes employed in the art are well known and generally comprise dyed or colored thermoplastic powders, known as toner particles, which are mixed with coarser carrier granules, such as ferromagnetic granules. The toner particles and carrier granules are selected such that the toner particles acquire the appropriate charge relative to the electrostatic latent image recorded on the photoconductive surface. When the developer mix is brought into contact with the charged photoconductive surface, the greater attractive force of the electrostatic latent image causes the toner particles to transfer from the carrier granules thereto. This concept was originally disclosed in US. Pat. NO. 2,297,691 issued to Carlson in 1942. Numerous other patents further amplify and describe the foregoing.

Many factors influence the quality of the developed image, one of the most significant factors being the introduction of contamination particles, i.e., dirt particles into the developer mix and in particular in the development zone. With the advent of multi-color electrophotographic printing, an additional problem is posed. In multi-color electrophotographic printing, a plurality of discretely colored toner particles are utilized therein. Each of the toner particles is arranged to produce a color complementary in color to that of the original document. Thus, should intermingling of the toner particles occur severe contamination in the development system will be the result. It is, therefore,evi-

toner particles from being distributed outside of the development system where they may contaminate other sub-components employed in the printing machine.

Accordingly, it is a primary object of the present invention to improve the development system by preventing particles from being expelled therefrom or being introduced therein.

SUMMARY OF THE INVENTION Briefly stated. and in accordance with the present in- 2 vention, there is. provided an apparatus for rendering visible an electrostatic latent image recorded on an image bearing member.

Pursuant to the present invention, the apparatus includes depositing means, actuating means, and sealing means. The depositing means is arranged to deposit charged particles onto the electrostatic latent image recorded on the image bearing member. The actuating means energizes the depositing means in response to the image bearing member being disposed at a presclected position. When energized,'the depositing means moves from an inoperative spaced from the image bearing member to an-operative position adjacent to the electrostatic latent image recorded thereon. The sealing means is operatively associated with the depositing means and adapted to prevent charged particles from being distributed external to the depositing means and the electrostatic latent image recorded on the image bearing member.

BRIEF DESCRIPTION OF THE DRAWINGS Other objects and advantages of the present invention will become apparent upon reading the following detailed description and upon reference to the drawings, in which:

FIG. 1 is a schematic perspective view of an electrophotographic printing machine embodying the features of the present invention therein;

FIG. 2 is a sectional elevational view of the development system employed in the FIG. 1 printing machine;

FIG. 3 is a fragmentary, sectional elevational view depicting one seal utilized in the FIG. 2 development system; and

FIG. 4 is a fragmentary, sectional elevational view depicting another seal used in the FIG. 2 development system.

While the present invention will hereinafter be described in conjunction with a preferred embodiment, it will be understood that it is not intended to limit the invention to that embodiment. On the contrary, it is intended to cover all alternatives, modifications and equivalentsas may be included within the spirit and scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION OF THE INVENTION With continued reference to the drawings wherein like reference numerals have been used throughout to designate like elements, FIG. 1 schematically illustrates a multi-color electrophotographic printing machine in which the present invention may be incorporated. The electrophotographic printing machine depicted schematically in FIG. 1 incorporates the various compophotoconductive surface 12 secured to and entrained.

thereabout. Photoconductive surface I2, preferably. is

ductive material is disclosed in U.S. Pat. No. 3,655,377 issued to Sechak in 1972. Drum rotates in the direction of arrow l4'to move photoconductive surface 12 sequentially through a series of processing stations. A timing disc is secured to the shaft on which drum 10 is mounted in the region of one end thereof. The timing disc coordinates the various machine operations with one another to produce the proper sequence of events at the appropriate processing station.

First, photoconductive surface 12 passes through charging station A which has positioned thereat a corona generating device, indicated generally at 16. Corona generating device 16 extends in a generally. transverse direction across photoconductive surface 12. This readily permits corona generating device 16 to charge photoconductive surface 12 to a relatively high substantially uniform potential. Preferably, corona generating device 16 is of the type described in U.S. Pat. No. 2,778,946 issued to Mayo in 1957.

Next, charged photoconductive surface 12 of drum 10 is rotated to exposure station B. Exposure station B includes a moving lens system, generally designated by the reference numeral 18, and a color filter mechanism, shown generally at 20. A suitable moving lens system is described in U.S. Pat. No. 3,062,108 issued to Mayo in 1962. An original document 22 is stationarily supported upon a transparent viewing platen 24. This enables successive incremental areas of original document 22 to be illuminated by moving lamp assembly 26. Lamp assembly 26 and lens system 18 as well as filter mechanism 20 move in a timed relation with drum 10 to scan successive incremental areas of original document 22 disposed upon platen 24. In this manner, a flowinglight image of original document 22 is projected onto charged photoconductive surface 12. The charge on photoconductive surface 12 is dissipated in accordance with the light intensity projected thereon. Filter mechanism 20 is adapted to interpose selective color filters into the optical light path. The appropriate color filter operates on the light rays passing through lens 18 to record an electrostatic latent image on photoconductive surface 12 corresponding to a preselected spectral region -of the electromagnetic wave spectrum, hereinafter referred to as a single color electrostatic latent image. I

After exposure, drum 10 rotates the single color electrostatic latent image recorded on photoconductive surface 12 to development station C. Development station C includes three developer units generally indicated by the reference numerals 28, 30, 32, respectively. The developer units are all of the type generally referred to as magnetic brush developer units. In a magnetic brush developer unit, a magnetizable developer mix having carrier granules and toner particles is continually brought through a directional flux field to form a brush of developer material. The developer mix is continually moving to provide fresh developer mix to the brush. Preferably, the brush in the magnetic brush system comprises a magnetic member with a mass of developer mix adhering thereto by magnetic attraction. The developer mix includes carrier granules having toner particles clinging thereto by triboelectric attraction. This chain-like arrangement of developer mix simulates the fibers of a brush. Development is achieved by bringing the brush of developer mix into contact with photoconductive surface 12. Each of the developer units 28, 30 and 32, respectively, apply toner particles to photoconductive surface 12 which are adapted to absorb light within a preselected spectral region of the electromagnetic wave spectrum corresponding to the wave length of light transmited through filter 20. For example, an electrostatic latent image formed by passing the light image through a green filter will record the red and blue portion of the spectrum as areas of relatively high charged density on photoconductive surface 12, while the green light rays will pass throughthe filter and cause the charge density on photoconductive surface 12 to be reduced to a voltage level substantially ineffective for development. The charged areas are then made visible by applying green absorbing (magenta) toner particles to the electrostatic latent image recorded on photoconductive surface 12. Similarly, a blue separation is developed with blue absorbng (yellow) toner particles,.while a red separation is developed with red absorbing (cyan) toner particles.

After development, the now visible toner powder image is moved to transfer station D. At transfer station D, the toner powder image is transferred to a sheet of final support material 34, such as plain paper, amongst other, by. means of a transfer drum, shown generally at 36. Transferdrum 36 rotates in the direction of arrow 38 and is adapted to have support material 34 secured thereto so as to be recirculated therewith. The surface of transfer drum 36 is electrically biased to a potential having sufficient magnitude and the proper polarity to electrostatically attract toner particles from photoconductive surface 12 to support sheet 34. A suitable electrically biased transfer drum is described in U.S. Pat. No. 3,612,677 issued to Langdon et al., in 1971. lnasmuch as support material 34 is secured releasably on transfer drum 36, successive toner powder images may be transferred thereto in superimposed registration with one another as drum 36 rotates through successive cycles.

After the last transfer operation, support sheet 34 is stripped from transfer drum 36. Gripper fingers 40 space support sheet 34 from drum 36 and gripper bar 42 is interposed therebetween. In this manner, support sheet 34 is separated from transfer drum 36. Thereafter, endless belt conveyor 44 advances suppport sheet 34 to fixing station E. Prior to proceeding with a detard roll 52, advances successive uppermost sheets 34 from stack 46 intochute 54. Chute 54 guides the advancing sheet into the nip between register rolls 56. Register rolls 56 align the sheet and forward it in registration with gripper fingers 40 to transfer drum 36 where it is secured thereon for recirculation therewith as hereinbefore described.

After the toner powder images have been transferred to support material 34, support material 34 is removed from drum 36 .and advanced to fuser 58 which permanently affixes the transferred powder image thereto. One typeof suitable fuser is described in U.S. Pat. No. 3,498,592 issued to Moser et al., in 1970. After the fusing process, support material 34 is advanced by endless belt conveyors 60 and 62 to catch tray 64 for subsequent removal from the machine by the operator.

Although a preponderance of the toner particles are transferred to support material 34, invariably residual toner particles remain on photoconductive surface 12 after the transfer of the toner powder image to support material 34. These residual toner particles are removed from photoconductive surface 12 as it moves through cleaning station E. Here, the residual toner particles are initially brought under the influence of a cleaning corona generating device (not shown) adaptd to neutralize the electrostatic charge remaining on photoconductive surface 12 and the residual toner particles. The neutralized toner particles are then cleaned from photoconductive surface 12 by a rotatably mounted fibrous brush 66 in contact therewith. A suitable brush cleaning device is described in U.S. Pat. No. 3,590,412 issued to Gerbasi in 1971.

It is believed that the foregoing description is sufficient for purposes of the present application to illustrate the general operation of an electrophotographic printing machine embodying the teachings of the present invention therein.

Referring now to the specific subject matter of the present invention, FIG. 2 depicts schematically the multicolor development system incorporated in the FIG. 1 printing machine. Development units 28, 30 and 32 are depicted therein in an elevational sectional view to indicate more clearly the various components included therewith. Only developer unit 28 will be described in detail as developer units 30 and 32 are substantially identical thereto, the distinction between each developer unit being the color the toner particles contained therein and minor geometrical differences due to the'mounting position. Developer unit 28 may ery thereof and is adapted to rotate so as to elevate developer mix 78 from the lower region of housing 68 to the upper region thereof. When developer mix 78' reaches the upper region of housing 68, it is lifted from the paddle wheel buckets to transport roll 72. Alternate buckets of paddle wheel 70 have apertures in the root diameter thereof so that developer mix carried in these areas is not moved to transport roll 72 but, in lieu thereof, returns to the lower region of developer housing 68. As developer mix 78 returns to the lower region of developer housing 68, it cascadesover shroud 80 which is ofa tubular configuration with an aperture 82 in the lower region thereof. Developer mix 78 is recirculated in this manner so that the carrier granules are continually agitated to mix with fresh particles. This generates a strong tribo-electric charge between the carrier granules and toner particles. As developer mix 78, in the paddle wheel buckets, approaches transport roll 72, the magnetic field produced by the fixed magnets therein attract developer mix 78. Transport roll 72- moves developer mix 78 in an upwardly direction by the frictional force exerted between the roll surface and developer mix. A surplus of developer mix 78 is furnished and metering blade 84 is provided to control the amount of developer mix 78 carried over the top of transport roll 72 and falls in a downwardly direction toward paddle wheel 70. It passes through the apertures of paddle wheel 70 in a downwardly direction into the lower region of developer housing 68.

The developer mix which passes metering blade 84 is carried over transport roll 72 to developer roll 74 and into development zone 86 located between photoconductive surface 12 and developer roll 74. When in the operative position, sealing means 76 is in contact with photoconductive surface 12 of drum 10 so as to form a seal between developer unit 28 and photoconductive surface 12. In this manner, the developer mix within the developer unit 28 is prevented from spreading to the remaining components of the printing machine external thereto. Moreover, contamination particles such as dust, dirt, etc., are not interposed in development zone 86 during development, thereby contaminating the resultant toner powder image produced on photoconductive surface 12. The sealing arrangement of the present invention will be described in greater detail with reference to FIGS. 3 and 4 hereinafter.

At the exit of development zone 86, the strong mag-. netic fields in a direction generally tangential to developer roll 74 continues to secure thereto the unused developer mix and denuded carrier granules. Upon passing from the development zone, the unused developer mix and denuded carrier granules enter a region relatively free from magnetic forces and fall from developer roll 74 in a downwardly direction into the lower region of developer housing 68. As the unused developer mix and denuded carrier granules descend, they pass through mixing baffle 88 which diverts the flow from the ends towards the center of developer housing 68 to provide mixing in this direction.

After the completed toner powder image has been recorded on photoconductive surface 12, development action is discontinued and the developer mix removed from contact with photoconductive surface 12. This is necessary in order to insure that subsequent images, which are to be developed with differently colored toner particles, are not affected by the prior toner particles. To achieve this, a suitable drive motor (not shown) is disconnected from paddle wheel 70, transport roll 72, and developer roll 74 stopping their rotation. This permits extended spring 90 to 'pivot developer housing 68 to the non-operative position thereof in which developer roll 74 is spaced from the electrostatic latent image recorded on photoconductive surface 12.

Cylindrical shroud 80 serves to control the fall of the unused developer mix and carrier granules such that they mix with the toner particles rather than simply falling into the lower region of developer housing 68. In addition, shroud 80 isolates, from the developer mix, an interior cylindrical enclosure which is used to house cylindrical toner dispenser 92. Toner dispenser 92 contains a fresh supply of toner particles which is dispensed through aperture 82 into the stream of developer mix 78. Additional toner particles are added to developer mix 78 to replace the toner particles used to form the toner powder images. This maintains the concentration of toner particles substantially constant to provide uniform color images on the sheet of support material.

As hereinbefore described, development is initiated when paddle. wheel is'actuated. Actuation of paddle 7 wheel 70 causes housing 68 to pivot about the center of paddle wheel 70. This is due to the reaction torque exerted by the restrainingforce of the developer mix on the movement of paddle wheel 70..ln this manner,developer housing 68 is pivoted to its operative position wherein developer roll 74 is closely adjacent to photoconductive wherein developer roll 74 is closely adjacent to photoconductive surface 12 enabling the toner particles to be attracted thereto producing a toner powder image thereon. After development is completed, paddle wheel 70 is de-energized and the force exerted by spring 90 pivots housing 68 to the inoperative position wherein developer roll 74 is spaced from photoconductivesurface 12.

In the preferred embodiment thereof, developer means or roll 74 includes a non-magnetic tubular member 94, preferably made from aluminum having an irregular or roughened exterior surface. Tubular member 94 is journaled for rotation by suitable means such as ball bearing mounts. A shaft 96, preferably made of steel, is concentrically mounted within tubular member 94 and serves as a fixed mounting for magnetic means 98. Magnetic means 98, preferably, comprises magnets made of barium ferrite in the form of annular rings and arranged with five poles on about a 284 are about shaft 96. Similarly, transport means or roll 72 includes a nonmagnetic tubular member 100, preferably made from aluminum having an irregular or roughened exterior surface. Tubular member 100 is journaled for rotation by suitable means such as ball bearing mounts. A shaft 102, preferably made of steel, is concentrically mounted within tubular member 100 and functions as a fixed mounting for magnetic means 104. Magnetic means 104, preferably, includes barium ferrite magnets in the form of annular rings arranged with four poles on about a 180 are about shaft 102.

The aforementioned operative procedure and apparatus described for developer unit 28 is applicable for developer units 30 and 32, respectively. The detailed structural arrangement of the developer units is more fully describedv in copending application Ser. No.

255,259 filed in 1972, the disclosure of which is hereby incorporated into the present application.

Referring now to sealing means 76, sealing means 76 includes end seals 106 and top seal 108. End seals 106 are depicted in FIG. 3 and top seal 108 is depicted in FIG. 4. End seals 106 are disposed on either side of developer housing 68 and positioned in the region of development zone 86. Preferably, end seal is a strip of polyethylene foam adapted to extend over the region of the sides of housing 68 extending in an outwardly direction therefrom. In this manner, end seals 68 engage photoconductive surface 12 of drum when housing 68 is pivoted to the operative position. This arrangement prohibits contamination particles from being introduced into development zone 86.'Moreover, it prohibits the expulsion of toner particles and developer mix from developer housing 68 in the region of the end thereof. End seals 106 may, preferably be secured to housing 68 by a suitable adhesive, or, in lieu thereof, by suitable fastening means.

Turning now to FIG. 4, top seal 108 includes a support member 110 and a brush 112 secured thereto. Support member 110 is formed of an L-shaped plastic member secured to housing 68 in the region of development zone 86. Brush 112 is attached to support member 110 by a suitable adhesive or fastener. Brush 112 includes a plurality of outwardly extending fibers. When housing 68 is pivoted to the operative position the fibers of brush 112 contact photoconductive surface 12 of drum 10. In this manner, the outward flow of toner particles to the remaining components of the printing machine is prevented, thereby preventing the degradation of their performance. By way of example, support member may be preferably made from a suitable elastomeric material. Similarly, brush 112 may be made from suitable synthetic fibers which will not disturb the toner powder image or from rabbit's fur.

While the present invention has, been described in connection with magnetic brush development. one skilled in the art will appreciate that the invention is not necessarily so limited and that other development systems may also be utilized. For example, in fur brush development, brush fibers replace carrier granules. When the brush is saturated with toner particles, the toner particles become charged triboelectrically. A soft fur is used in the form of a cylindrical brush. Toner particles are fed continuously to the brush which, when activated, moves from its inoperative position spaced from the photoconductive surface to its operative position in communication therewith. Similarly, powder cloud systems, cascade systems, paddle wheel systems, etc., may also be employed.

In recapitulation, it is apparent that the development systemof the present invention prevents particles from the developer mix, i.e., carrier granules or toner particles from leaving the development system and contaminating the remaining components of the electrophotographic printing machine. It is apparent from the foregoing that the sealing apparatus of the present invention provides a two-fold advantage, it eliminates contamination in the development zone so as to insure that the toner powder images remain substantially pure, and prevents contamination of the remaining machine com ponents which would result in degradation of their performance. Thus, the foregoing development system is a substantial improvement over devices hereinbefore utilized.

It is, therefore, evident that there has been provided in accordance with this invention, an apparatus for developing an electrostatic latent image that fully satisfies the objects, aims and advantages set forth above. While this invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims.

What is claimed is:

1. An apparatus for rendering vvisible an electrostatic latent image recorded on an image bearing member, including:

means for depositing charged particles onto the electrostatic latent image recorded on the image bearing member,'said depositingmeans comprising a housing defining a chamber adapted to store the charged particles therein, means for advancing the charged particles from a first region to a second region for discharge thereat, rotary driven developer means mounted within the chamber of said housing closely proximate to said advancing means for receiving the charged particles therefrom, said developer means being arrangedto deposit the charged particles onto the electrostatic latent image when in operative communication therewith, means for driving said advancing means such that the reaction torque to the driving moment applied to said advancing means pivots said housing disposing said developer means adjacent the electrostatic latent image in operative communication therewith;

means for actuating said depositing means in response to the image bearing member being disposed at a preselected position, said depositing means moving from an inoperative position spaced from the image bearing member to an operative position adjacent to the electrostatic latent image recorded thereon;

biasing means for resiliently urging said depositing means from the operative position adjacent the electrostatic latent image to the inoperative position spaced from the image bearing member; and

sealing means, operatively associated with said depositing means, for preventing charged particles from being distributed external to said depositing means and the image bearing member when said depositing means is located in the operative position.

2. An apparatus as recited in claim 1, wherein said sealing means includes:

a support member mounted in at least the region of one end of the periphery of said housing;

a brush secured to said support member, said brush having a plurality of flexible fibers extending in a substantially outwardly direction from said support member and being adapted to contact the image bearing member when said housing pivots to the operative position; and

a pair of resilient strips mounted in the region of either side ofthe periphery of said housing, said resilient strips being adapted to contact the image'bearing member when said housing pivots to the operative position, thereby preventing, in combination with said brush, charge particles from being distributed externally of said developer means and the electrostatic latent image recorded on the image bearing member.

3. An apparatus as recited in claim 2, wherein said advancing means includes:

conveyor means mounted for movement within the chamber of said housing and arranged to move the charged particles from a first region to an intermediate region; and

rotary driven transport means mounted within the chamber of said housing and arranged to move the charged particles from the intermediate region of the second region for discharge thereat.

4. An apparatus as recited in claim 3, wherein:

said transport means includes a first tubular member of non-magnetic material and first magnetic means fixedly disposed within said first tubular member for creating a magnetic field in the path of the periphery of said firsttubular member; and

said developer means includes a second tubular member of non-magnetic material and second magnetic means fixedly disposed within said second tubular member for creating a magnetic field in the path of the periphery of said second tubular member. 7

5. An electrophotographic printing machine of the type having a photoconductive member, a corona gencrating device adapted to charge the photoconductive member to a substantially uniform level, and an exposure mechanism for projecting a light image of an original document onto the charged photoconductive member to record an electrostatic latent image thereof, wherein the improvement includes:

means for depositing toner particles onto the electrostatic latent image recorded on the photoconductive member, said depositing means comprising a developer housing defining a chamber storing a developer mix comprising carrier granules and toner particles, means for advancing the developer mix from a first region to a second region for discharge thereat, rotary driven developer means mounted within the chamber of said developer housing closely proximate to said advancing means for receiving the developer mix therefrom, said developer means being arranged to deposit toner particles onto the latent image when in operative communication therewith, means for driving said advancing means such that the reaction torque to the driving moment applied to said advancing means pivots said developer housing disposing said developer means adjacent the electrostatic latent image in operative communication therewith; means for actuating said toner depositing means in response to the photoconductive member being disposed at a preselected position, said toner depositing means moving from an inoperative position spaced from the photoconductive member to an operative position adjacent to the electrostatic latent image; biasing means for resiliently iting means from the operative position adjacent the electrostatic latent image to the inoperative position spaced from the photoconductive member; and sealing means, operatively associated with said toner depositing means, for preventing toner particles from being distributed external to said toner depositing means and the photoconductive member when said toner depositing means is located in the operative position. 6. A printing machine as recited in claim 5, wherein said sealing means includes:

a support member mounted in at least the region of one end of the periphery of said developer housing; a brush secured to said support member, said brush having a plurality of flexible fibers extending in a substantially outwardly direction from said support member and being adapted to contact the photoconductive member when said developer housing pivots to the operative position; and a pair of resilient strips mounted in the region of either, side of the periphery of said housing, said resilient strips being adapted to contact the photoconductive member when said developer housing pivots to the operative position, thereby preventing, in combination with said brush, toner particles from being distributed externally of said developer means and the electrostatic latent image recorded on the photoconductive member. 7. A printing machine as recited in claim 6, wherein said advancing means includes:

conveyor means mounted for movement within the chamber of said developer housing and arranged to urging said toner depos-.

fixedly disposed within said first tubular member 5 for creating a magnetic field in the path of the pe-.

riphery of said first tubular member; and

said developer means includes a second tubular member of non-magnetic material and second magnetic means fixedly disposed within said tubular member for creating a magnetic field in the path of the periphery of said second tubular member. 

1. An apparatus for rendering visible an electrostatic latent image recorded on an image bearing member, including: meAns for depositing charged particles onto the electrostatic latent image recorded on the image bearing member, said depositing means comprising a housing defining a chamber adapted to store the charged particles therein, means for advancing the charged particles from a first region to a second region for discharge thereat, rotary driven developer means mounted within the chamber of said housing closely proximate to said advancing means for receiving the charged particles therefrom, said developer means being arranged to deposit the charged particles onto the electrostatic latent image when in operative communication therewith, means for driving said advancing means such that the reaction torque to the driving moment applied to said advancing means pivots said housing disposing said developer means adjacent the electrostatic latent image in operative communication therewith; means for actuating said depositing means in response to the image bearing member being disposed at a preselected position, said depositing means moving from an inoperative position spaced from the image bearing member to an operative position adjacent to the electrostatic latent image recorded thereon; biasing means for resiliently urging said depositing means from the operative position adjacent the electrostatic latent image to the inoperative position spaced from the image bearing member; and sealing means, operatively associated with said depositing means, for preventing charged particles from being distributed external to said depositing means and the image bearing member when said depositing means is located in the operative position.
 2. An apparatus as recited in claim 1, wherein said sealing means includes: a support member mounted in at least the region of one end of the periphery of said housing; a brush secured to said support member, said brush having a plurality of flexible fibers extending in a substantially outwardly direction from said support member and being adapted to contact the image bearing member when said housing pivots to the operative position; and a pair of resilient strips mounted in the region of either side of the periphery of said housing, said resilient strips being adapted to contact the image bearing member when said housing pivots to the operative position, thereby preventing, in combination with said brush, charge particles from being distributed externally of said developer means and the electrostatic latent image recorded on the image bearing member.
 3. An apparatus as recited in claim 2, wherein said advancing means includes: conveyor means mounted for movement within the chamber of said housing and arranged to move the charged particles from a first region to an intermediate region; and rotary driven transport means mounted within the chamber of said housing and arranged to move the charged particles from the intermediate region of the second region for discharge thereat.
 4. An apparatus as recited in claim 3, wherein: said transport means includes a first tubular member of non-magnetic material and first magnetic means fixedly disposed within said first tubular member for creating a magnetic field in the path of the periphery of said first tubular member; and said developer means includes a second tubular member of non-magnetic material and second magnetic means fixedly disposed within said second tubular member for creating a magnetic field in the path of the periphery of said second tubular member.
 5. An electrophotographic printing machine of the type having a photoconductive member, a corona generating device adapted to charge the photoconductive member to a substantially uniform level, and an exposure mechanism for projecting a light image of an original document onto the charged photoconductive member to record an electrostatic latent image thereof, wherein the improvement includes: means for depositing toner particles onto the electrostatic latent image recorded on the photoconductive member, said depositing means comprising a developer housing defining a chamber storing a developer mix comprising carrier granules and toner particles, means for advancing the developer mix from a first region to a second region for discharge thereat, rotary driven developer means mounted within the chamber of said developer housing closely proximate to said advancing means for receiving the developer mix therefrom, said developer means being arranged to deposit toner particles onto the latent image when in operative communication therewith, means for driving said advancing means such that the reaction torque to the driving moment applied to said advancing means pivots said developer housing disposing said developer means adjacent the electrostatic latent image in operative communication therewith; means for actuating said toner depositing means in response to the photoconductive member being disposed at a preselected position, said toner depositing means moving from an inoperative position spaced from the photoconductive member to an operative position adjacent to the electrostatic latent image; biasing means for resiliently urging said toner depositing means from the operative position adjacent the electrostatic latent image to the inoperative position spaced from the photoconductive member; and sealing means, operatively associated with said toner depositing means, for preventing toner particles from being distributed external to said toner depositing means and the photoconductive member when said toner depositing means is located in the operative position.
 6. A printing machine as recited in claim 5, wherein said sealing means includes: a support member mounted in at least the region of one end of the periphery of said developer housing; a brush secured to said support member, said brush having a plurality of flexible fibers extending in a substantially outwardly direction from said support member and being adapted to contact the photoconductive member when said developer housing pivots to the operative position; and a pair of resilient strips mounted in the region of either side of the periphery of said housing, said resilient strips being adapted to contact the photoconductive member when said developer housing pivots to the operative position, thereby preventing, in combination with said brush, toner particles from being distributed externally of said developer means and the electrostatic latent image recorded on the photoconductive member.
 7. A printing machine as recited in claim 6, wherein said advancing means includes: conveyor means mounted for movement within the chamber of said developer housing and arranged to move the developer mix from a first region to an intermediate region; and rotary driven transport means mounted within the chamber of said developer housing and arranged to move the developer mix from the intermediate region to the second region for discharge thereat.
 8. A printing machine as recited in claim 7, wherein: said transport means includes a first tubular member of non-magnetic material and first magnetic means fixedly disposed within said first tubular member for creating a magnetic field in the path of the periphery of said first tubular member; and said developer means includes a second tubular member of non-magnetic material and second magnetic means fixedly disposed within said tubular member for creating a magnetic field in the path of the periphery of said second tubular member. 